Sniffing Entrapped Humans with Sensor Arrays

TLDR

Earthquakes are lethal natural disasters frequently burying people alive under collapsed buildings. Tracking entrapped humans from their unique volatile chemical signature with hand‑held devices would accelerate urban search and rescue efforts. The pilot study employs compact orthogonal arrays of three nanostructured metal‑oxide sensors (Si‑doped WO3, Si‑doped MoO3, Ti‑doped ZnO) tailored for sensitive detection of breath‑ and skin‑emitted metabolic tracers acetone, ammonia, isoprene, CO₂, and relative humidity, supplemented by commercial CO₂ and humidity sensors. In plethysmography chamber tests simulating entrapment, the array rapidly detected sub‑ppm acetone, ammonia, and isoprene with high accuracies (19, 21, 3 ppb) and precision, matching benchtop SRI‑TOF‑MS (Pearson ≥ 0.9) and proving an inexpensive, portable sensor array suitable for hand‑held or drone detectors to screen terrain quickly.

Abstract

Earthquakes are lethal natural disasters frequently burying people alive under collapsed buildings. Tracking entrapped humans from their unique volatile chemical signature with hand-held devices would accelerate urban search and rescue (USaR) efforts. Here, a pilot study is presented with compact and orthogonal sensor arrays to detect the breath- and skin-emitted metabolic tracers acetone, ammonia, isoprene, CO2, and relative humidity (RH), all together serving as sign of life. It consists of three nanostructured metal-oxide sensors (Si-doped WO3, Si-doped MoO3, and Ti-doped ZnO), each specifically tailored at the nanoscale for highly sensitive and selective tracer detection along with commercial CO2 and humidity sensors. When tested on humans enclosed in plethysmography chambers to simulate entrapment, this sensor array rapidly detected sub-ppm acetone, ammonia, and isoprene concentrations with high accuracies (19, 21, and 3 ppb, respectively) and precision, unprecedented by portable sensors but required for USaR. These results were in good agreement (Pearson's correlation coefficients ≥0.9) with benchtop selective reagent ionization time-of-flight mass spectrometry (SRI-TOF-MS). As a result, an inexpensive sensor array is presented that can be integrated readily into hand-held or even drone-carried detectors for first responders to rapidly screen affected terrain.